1. Field of the Invention
The present invention relates to a method of manufacturing a foamed product having a convexo-concave surface in which a foaming inhibitor is coated on or infiltrated into a surface of a foamable preform made of a foamable resin composition in a prescribed pattern and then the preform is foamed, and it further relates to a foamed product obtained through such a method and a material usable for such a method.
More specifically, the present invention relates to a liquid toner containing a foaming inhibitor, a method of a foamed product having a convexo-concave pattern involving a step where the foaming inhibitor is coated on or infiltrated into a surface of the foamable preform in a prescribed pattern though an electrostatic technique such as an electrostatic record or an electrostatic image transfer, and further relates to an intermediate product and a convexo-concave foamed product obtained though such a method.
2. Description of the Related Art
There has been known a printed product, an interior material and building material having a three dimensional pattern or a relief pattern, such as a foamed wall paper, a foamed flooring material or the like. They have been manufactured by a xe2x80x9cchemical embossxe2x80x9d process. In the chemical emboss process, a foaming inhibitor is applied on a surface of a foamable preform made of a foamable resin composition in a prescribed pattern to form a pattern of a coating or infiltrated portion containing the foaming inhibitor, and then the foamable preform is foamed by heating or another manner. Thus a portion of the preform with no foaming inhibitor is foamed to rise or bulge while the other portion of the preform at which the foaming inhibitor is present is not foamed to be left unchanged, thereby forming a foamed product which has a surface provided with a convexo-concave pattern. The thus formed convexo-concave pattern is according to the pattern of the applied foaming inhibitor, and it makes up a three dimensional pattern (or a relief pattern) provided on the surface of the foamed product. The printed product and the other articles having a three dimensional pattern is manufactured through such a chemical emboss process. The chemical emboss process is disclosed in Japanese Patent Publication(Kohkoku) Nos. Sho 43(1968)-28636 and Japanese Patent Publication(Kohkoku) Nos. Sho 47(1972)-29187.
One of the known foamable resin composition is composed of polyvinyl chloride resin, a foaming agent such as azodicarbonamide, and a foaming accelerator such as zinc naphthenate. The foaming agent such as azodicarbonamide is decomposed by heating and generates gases such as carbon dioxide to form bubbles in the foamable resin composition. The foaming accelerator such as zinc naphthenate acts as a catalyst for decomposition of the foaming agent to lower a decomposition temperature. On the other hand, there has been used, as the foaming inhibitor, benzotriazole compounds or the like capable of inhibiting an effect of the foaming accelerator. When the foaming inhibitor is applied on the surface of the foamable preform made of the foamable resin composition, a foaming temperature of the portion retaining the foaming inhibitor gets higher than that of the other portion of the surface with no foaming inhibitor. Accordingly, if heating temperature of the foamable preform is controlled within at least a foaming temperature of the portion retaining no foaming inhibitor while under a foaming temperature of the portion retaining the foaming inhibitor, it is possible to foam only at the portion retaining no foaming inhibitor.
In the known art, the foaming inhibitor has been patternwise applied on the surface of the foamable preform by gravure printing, offset printing or the like, which need to use a form plate. Such a conventional process accordingly has suffered from a relatively long time and a large cost to make the form plate, whereby it has been involved in a problem that it is impossible to make preparation and evaluation of a prototype quick or smooth in a research and development stage.
As the other method substituting for the actual preparation of the prototype, it may be worth while considering a method in which a design of the surface of the prototype is generated and reproduced on a monitor through a digital process, and the thus reproduced image of the design is quickly output by means of an on-demand type printer such as an electrostatic plotter, an electrophotographic printer or the like to obtain a two dimensional sample of the design. When a sample of an ordinary printed product or publication is required, it is possible to generate and output an image very similar to a true image of a final product or a prototype in a short time by means of some digital proof printer, thereby carrying out preparation and evaluation of the proof in a sufficient mobility. However, since the foamed product having a convexo-concave surface largely varies its design or appearance including impression, texture or the like through the foaming process, even the digital proof printer can not generate the image very similar to the surface design of the final product or prototype. Accordingly it has been impossible to carry out an exact evaluation of the foamed product by this method.
For that reason, a designer or another product developer who studies the foamed product having a three dimensional pattern such as the wall paper, the foamed flooring or the like has not been allowed to prepare the prototypes frequently in the development stage, while he has been usually checked nothing but a montage image which is output by the digital proof printer and however reproduced not so exactly in order to perform the product development, and therefore it has been difficult to evaluate the design of the convexo-concave pattern of the surface in detail.
In addition, it is desirable for presentation of the foamed product to use a sample same as or very similar to an actual final product so as to demonstrate the design thereof sufficiently to the user. Preparation of the exact sample however needs to prepare the form plate for applying of the foaming inhibitor, thereby causing difficulties in time schedule and cost. Therefore, it has been difficult to perform the presentation of the foamed product in a sufficient mobility.
An object of the present invention is to easily and quickly form a coating or infiltrated portion containing the foaming inhibitor in a desired pattern on a surface of a foamable preform without the use of the form plate, but by means of an on-demand type printer such as an electrostatic plotter, an electrophotographic printer or the like.
To attain the above object, the present invention provides a liquid toner in which toner particles containing a foaming inhibitor are dispersed. Further, the present invention provides methods for producing such a liquid toner. Still further, the present invention provides methods for manufacturing a foamed product having a convexo-concave pattern and an intermediate product thereof, in which the foaming inhibitor is made adhere on or infiltrate into a surface of a foamed preform via an on-demand type printing method. Still further, the present invention provides the convexo-concave foamed product and the intermediate product thereof manufactured by such methods.
The liquid toner of the present invention comprises fine particles containing a foaming inhibitor affecting a foamable resin composition and an electrically insulating dispersion medium, wherein the fine particles are dispersed in the electrically insulating dispersion medium.
In one preferred embodiment, the liquid toner of the present invention comprises copolymer resin particles and an electrically insulating dispersion medium, the copolymer resin particles containing a copolymer resin composed of at least two different monomer components including a first and a second monomer components and a foaming inhibitor affecting a foamable resin composition, and the copolymer resin particles being dispersed in the electrically insulating dispersion medium,
wherein said copolymer resin and said electrically insulating dispersion medium are related to each other such that (i) a difference xcex94(xcex4p1xe2x88x92xcex4d) between a solubility parameter value xcex4p1 of a homopolymer composed only of the first monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not smaller than 1.0, (ii) a difference xcex94(xcex4p2xe2x88x92xcex4d) between a solubility parameter value xcex4p2 of a homopolymer composed only of the second monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not larger than 1.0, and (iii) a difference xcex94(xcex4p1xe2x88x92p2) between the two solubility parameter values xcex4p1 and xcex4p2 of those homopolymers is at least 0.5, and
each of said copolymer resin particles has a configuration in which a core portion insoluble in the electrically insulating dispersion medium is surrounded with an outer skin portion soluble or swellable in the electrically insulating dispersion medium.
In such a liquid toner, trimellitic anhydride and/or benzotriazole is preferably used as the foaming inhibitor.
The above described liquid toner may be produced in such manner that resin particles are precipitated out from a liquid dissolving or dispersing the foaming inhibitor and the resin therein by taking change of solubility of the used resin. Each precipitated resin particle has a configuration in which a surface of a fine particle of a foaming inhibitor is covered with a resin and also has capability to be dispersed in an electrically insulating dispersion medium
One preferred producing method comprises the steps of:
providing a solution prepared by dissolving or dispersing a copolymer resin composed of at least two different monomer components including a first and a second monomer components in the solvent;
further providing the electrically insulating dispersion medium being related to the copolymer resin such that (i) a difference xcex94(xcex4p1xe2x88x92xcex4d) between a solubility parameter value xcex4p1 of a homopolymer composed only of the first monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not smaller than 1.0, (ii) a difference xcex94(xcex4p2xe2x88x92xcex4d) between a solubility parameter value xcex4p2 of a homopolymer composed only of the second monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not larger than 1.0, and (iii) a difference xcex94(xcex4p1xe2x88x92xcex4p2) between the two solubility parameter values xcex4p1 and xcex4p2 of those homopolymers is at least 0.5;
mixing the solution of the copolymer resin with the dispersion medium in the presence of the foaming inhibitor affecting a foamable resin composition with a condition keeping a dispersed state of the foaming inhibitor; and
removing the solvent from the mixture after mixing of the dispersion medium.
In the above mentioned method, the liquid toner is produced by mixing a solution of the copolymer resin in a good solvent such as toluene with the electrically insulating dispersion medium in the presence of the foaming inhibitor such as trimellitic anhydride to cause granulation of the copolymer resin particles, and then removing the good solvent as required.
The electrically insulating dispersion medium to be preferably used in the present invention has a solubility parameter value (SP value) defined as xe2x80x9cxcex4d xe2x80x9d, and xcex4d of the dispersion medium has a relationship such that a difference xcex94(xcex4p1xe2x88x92xcex4d) between a solubility parameter value xcex4p1 of a homopolymer composed only of the first monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not smaller than 1.0, and that a difference xcex94(xcex4p2xe2x88x92xcex4d) between a solubility parameter value xcex4p2 of a homopolymer composed only of the second monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not larger than 1.0. That is, the dispersion medium to be used in the present invention has a low affinity to the first monomer component of the copolymer resin, while has a high affinity to the second monomer component of the copolymer resin. In addition, a difference xcex94(xcex4p1xe2x88x92xcex4p2) between the two solubility parameter values xcex4p1 and xcex4p2 of those homopolymers is at least 0.5. Accordingly, there is a considerable gap between the affinity presented for the portion of the first monomer component by the dispersion medium and the other affinity presented for the portion of the second monomer component by the dispersion medium.
For that reason, when a solution or varnish containing the above described copolymer resin composed of at least the first and the second monomer components is mixed with the electrically insulating dispersion medium having such a characteristics of SP value as described above in the presence of the foaming inhibitor which is essentially little in affinity to the electrically insulating dispersion medium, a portion of the first monomer component in the copolymer resin is repelled by the dispersion medium to be adsorbed on or adhere to a surface of the foaming inhibitor. As the result, the copolymer resin microscopically aggregates so as to surround the foaming inhibitor serving as a core, thereby foaming the copolymer resin particles containing the foaming inhibitor.
Each of the copolymer resin particle thus formed is composed of a core portion which is insoluble in the dispersion medium and an outer skin portion which is soluble or swellable in the dispersion medium and surrounding the core portion. The core portion is composed mainly of the foaming inhibitor and portions which are incorporated in a molecule of the copolymer resin and have a high affinity to the foaming inhibitor, particularly the first monomer component. On the other hand, the outer skin portion is composed mainly of portions which are incorporated in a molecule of the copolymer resin and have a high affinity to the electrically insulating dispersion medium, particularly the second monomer component. Since the copolymer resin particles have such a configuration, particles of the foaming inhibitor as the core are prevented from coming into a direct contact with each other and stably dispersed in the dispersion medium, thus preventing occurrence of precipitation or a macroscopic aggregation of the copolymer resin particles. In addition, the liquid toner of the present invention also has a good electrification characteristics. Accordingly, when an electrostatic latent image is developed with the use of the liquid toner of the present invention, a pattern coincident with the latent image and containing the foaming inhibitor can be made.
The liquid toner containing the foaming agent may be produced the other method. For example, the other preferred method may comprise the steps of:
providing the foaming inhibitor affecting a foamable resin composition;
further providing a copolymer resin composed of at least two different monomer components including a first and a second monomer components;
further providing the electrically insulating dispersion medium being related to the copolymer resin such that (i) a difference xcex94(xcex4p1xe2x88x92xcex4d) between a solubility parameter value xcex4p1 of a homopolymer composed only of the first monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not smaller than 1.0, (ii) a difference xcex94(xcex4p2xe2x88x92xcex4d) between a solubility parameter value xcex4p2 of a homopolymer composed only of the second monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not larger than 1.0, and (iii) a difference xcex94(xcex4p1xe2x88x92xcex4p2) between the two solubility parameter values xcex4p1 and xcex4p2 of those homopolymers is at least 0.5;
adding the copolymer resin in the dispersion medium and dissolving it by heating, while adding the foaming agent in the dispersion medium at the same time or a different time and dispersing it to prepare a heated mixture containing the dissolved copolymer resin and the dispersed foaming agent; and
cooling the heated mixture.
In the present invention, a foamable intermediate product can be manufactured by: (1) providing a foamable preform having a foamable portion made of a foamable resin composition; (2) further providing a recording material containing a foaming inhibitor which is usable for a printing method based on an on-demand system capable of outputting an image directly on an receiving material according to electric, thermal or optical record signals; and then (3) applying the recording material on the foamable preform by the printing method based on an on-demand system to make the recording material containing the foaming inhibitor adhere on or infiltrate into a surface of the foamable portion in a prescribed pattern.
Further, when the foamable portion of the thus prepared foamable intermediate product is foamed by, for example, heating, a surface of the intermediate product is formed into a convexo-concave pattern, thereby obtaining a foamed product of the present invention.
In one preferred embodiment, the manufacturing method comprises the steps of:
providing the foamable preform having a foamable portion made of a foamable resin composition;
further providing a liquid toner, as said recording material, in which copolymer resin particles are dispersed in an electrically insulating dispersion medium, the copolymer resin particles containing a copolymer resin composed of at least two different monomer components including a first and a second monomer components and a foaming inhibitor affecting the foamable resin composition, the copolymer resin and the electrically insulating dispersion medium being related to each other such that (i) a difference xcex94(xcex4p1xe2x88x92xcex4d) between a solubility parameter value xcex4p1 of a homopolymer composed only of the first monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not smaller than 1.0, (ii) a difference xcex94(xcex4p2xe2x88x92xcex4d) between a solubility parameter value xcex4p2 of a homopolymer composed only of the second monomer component in the copolymer resin and a solubility parameter value xcex4d of the electrically insulating dispersion medium is not larger than 1.0, and (iii) a difference xcex94(xcex4p1xe2x88x92xcex4p2) between the two solubility parameter values xcex4p1 and xcex4p2 of those homopolymers is at least 0.5, and each of said copolymer resin particles having a configuration in which a core portion insoluble in the electrically insulating dispersion medium is surrounded with an outer skin portion soluble or swellable in the electrically insulating dispersion medium;
subjecting the foamable preform to an electrostatic record or an electrostatic image transfer with the use of the liquid toner to apply the copolymer resin particles on a surface of the foamable portion in a prescribed pattern; and
foaming the foamable portion after the applying of the copolymer resin particles to form the surface of the foamable portion into a convexo-concave pattern.
Since the use of the liquid toner of the present invention can form a pattern of the foaming inhibitor in accordance with the electrostatic latent image, any image-forming technique utilizing an effect of the electrostatic force, particularly an electrostatic record and an electrostatic image transfer, has come adaptable for formation of a pattern of a foamed or nonfoamed portion.
According to the manufacturing method of the present invention, an original image for the convexo-concave pattern, for example, a pattern imitating some natural article such as grain of wood or stone and an artificial pattern can be generated easily and quickly through a digital process, and then a pattern of the foaming inhibitor coincident with the thus generated original image can be easily and quickly formed on a surface of the foamable preform by the electrostatic record or the electrostatic image transfer. This manufacturing method does not require a step preparing the form plate. Therefore, it is possible to manufacture the foamed product having a convexo-concave pattern without so much time and trouble. In particular, the present invention including the liquid toner and the manufacturing method is fit to, for example, prepare prototypes frequently, prepare a sample in a hurry for completely progressing a schedule of a presentation, and otherwith, produce and supply various kinds of convexo-concave foamed products by a small quantity on some system of production on orders.